1. Field of the Invention
The present invention relates to a method of the development of an electrostatic image. More particularly, the present invention relates to an improvement in the development of an electrostatic image with a magnetic brush of a magnetic developer, in which earing of a magnetic brush is highly improved.
2. Description of the Prior Art
As the conventional developer for use in developing an electrostatic image with a magnetic brush, there can be mentioned two types of developers, that is, a two-component type developer comprising a mixture of a fixable electroscopic powder (toner) and a magnetic carrier and a one-component type developer comprising particles formed by shaping a dispersion of a powder of a magnetic material in a fixing binder medium.
In the two-component type developer, it is indispensable that toner particles should be charged by friction between the magnetic carrier and the toner, and the two-component type developer is defective in that a good image cannot be obtained unless the mixing ratio of the magnetic carrier to the toner is within a certain range. Moreover, while the two-component type developer is used for a long time, the toner or a component of the toner is accumulated on the surface of the magnetic carrier (ordinarily called "spent toner") and charging of the toner becomes difficult.
The one-component type developer is advantageous in that development is possible without a trouble of the use of the magnetic carrier which is indispensable for the two-component type developer. However, when the one-component type developer is used, earing of the magnetic brush is considerably changed according to changes of environmental conditions such as the temperature and the humidity, and it often is difficult to keep the amount of the ear of the magnetic brush constant. More specifically, in case of the one-component type magnetic developer, the ear of the magnetic brush is formed of the developer per se, and since earing is effected while developer particles are being moved on a development sleeve with rotation of the development sleeve or rotation of a magnet arranged in the development sleeve, if the flowability of the developer (which is changed according to changes of environmental conditions) is changed, the amount of the ear is changed.